1. Field of the Invention
The present invention relates to a method and apparatus for adhesion of a semiconductor substrate in order to make a semiconductor substrate adhere to a support block with an adhesive.
2. Related Art
In recent years, a trend of super-integration of a semiconductor integrated circuit has been accelerated and in company with the trend, not only has a semiconductor substrate been larger in diameter, but miniaturization in a semiconductor device has also progressed toward to a finer design rule. For this reason, requirement for a flatness of a semiconductor substrate has increasingly been severer.
A flatness of a semiconductor substrate is dependent on an adhesion accuracy of a semiconductor substrate to a support block (pressure plate) in polishing of the semiconductor substrate. There has conventionally been conceived an adhesion method as described in Publication of Unexamined Japanese Patent Application No. 64-10643.
The adhesion method will be described in reference to FIG. 8. In the adhesion method, an adhesive material 23, such as wax, an adhesive or the like, is applied on a semiconductor substrate 21 or a support block 22 of a polishing apparatus, the semiconductor substrate 21 is vacuum chucked on a porous suction plate 25 made of ceramics or the like which is mounted to a suction member 24, the semiconductor substrate 21 is pressed on the support block 22 while the support block 22 is heated and the adhesive material 23 is maintained in a molten state and thereafter, vacuum suction is broken. A suction surface of the suction plate 25 used in this case is a spherical surface.
There has been an established understanding on the following effects thereof according to such a method.
The method is conducted in the following way: the semiconductor substrate 21 is pressed on the support block 22 and vacuum chucking of the semiconductor substrate 21 is broken, in other words, the semiconductor substrate 21 is released from a curved condition while the semiconductor substrate 21 is pressed, thereby the semiconductor substrate 21 changes a profile of the current curved surface and the surface gradually restores its original flat one while the restoration progresses from the central region to its periphery along a radial direction or from one region to another region along one direction so that, for example, a surface of the semiconductor substrate 21 pressing the support block 22 grows to a larger circle area from a small one at its center as a starting. Therefore, even when bubbles are mixed in the adhesive material 23, the bubbles are pressed out radially or along the one direction. If the curved condition of the semiconductor substrate 21 is released in the above mentioned manner, a pressing force is kept constant including a restored surface area in a radial direction or in one direction in the course of restoration of the original profile. Therefore, mixing-in of bubbles to an adhesive material is effectively prevented.
In the above mentioned method, however, since a porous suction plate 25 is used, minute concave or convex portions arise on the semiconductor substrate 21, which is vacuum chucked. Therefore, mixing-in of bubbles to the adhesive material 23 is unavoidable when the semiconductor substrate 21 is pressed on the support block 22. Moreover, part of the bubbles remains in the adhesive material 23 after adhesion of the semiconductor substrate 21 to the support block 22 is finished. As a result, part of the minute concave or convex portions are transferred on the semiconductor substrate 21, which has caused a problem of reduction in flatness level.